Earlier quoted context omitted.
Why first principles? Create a do-not-mail list. Make up the funding gap with taxes.
I would like to see a fee for unsolicited bulk mail senders to help pay for the service, along with a "do not mail" list. I would prefer that nobody subsidies the delivery of landfill to my mailbox.
The USPS literally has a service "deliver this flyer to every residential mailbox in this ZIP". It's cheaper per-item than a letter, yes, but the margins on "stuff a bunch of identical objects into N boxes" are much higher than "figure out which of N boxes this 1 unique mailpiece goes to".